This disclosure relates to advanced image signal processing technology including encoded signals and digital watermarking. One claim recites a printed object comprising a machine-readable signal therein, the printed object comprising: a substrate; a first color printed on a substrate, the first color printed on the substrate so as to include holes without the first color, the holes arranged corresponding to the 2-d spatial pattern representing the machine-readable signal; a second color printed in the holes, in which the first color and the second color comprise a spectral reflectance difference at or around 660nm in the range of 8%-60%, in which the second color is printed in the holes with a trap of 1-4 pixels, and in which the machine-readable signal is detectable from image data captured with red-light illumination, the red-light illumination comprising a peak illumination at or around 660nm, in which the trap comprises a spread trap, in which the second color overlaps the first color. The technology may be applied to retail packages and other printed objects, e.g., such as hang tags, labels and receipts.